Issue backdrop-contrib#51: Revert breaking change.

By @indigoxela

og.module

@@ -2118,13 +2118,6 @@ function og_group($group_type, $gid, $values = array(), $save_created = TRUE) {
     // Save the membership for update, or if the OG membership is new when
     // "save-created" is TRUE.
     $og_membership->save();
-
-    // Also populate the group audience field on the entity for data
-    // consistency.
-    // @see https://www.drupal.org/project/og/issues/2148047
-    if ($field_name) {
-      $wrapper->{$field_name}[] = $gid;
-    }
   }
 
   return $og_membership;